Friday, January 6, 2012

Mold making, cheap and easy.

So you wanna make a silicone mold, but don't want to spend oodles of dollars on expensive silicone?

Well you are just in luck as I learned how to do such a thing when I got my fancy art degree.

Now this is a soft mold. So you probably don't want to be casting soft things in it (silicone, latex, etc.).

A general rule I follow (but as with any rule there are exceptions) is that you don't cast like into like, for example hard in to hard or soft into soft. So you don't make a plaster mold and then cast fiberglass into it. Unless you are making a one off mold and don't care that you'll have to break the mold to get the piece out. Conversely, casting silicone into a silicone mold is a bad idea. Why, you ask? Well silicone has this amazing property to stick to itself. So don't do it. Latex doesn't really stick to silicone, casting latex works better into something like porous so just use something like hydrostone or ultracal.
Here is what you will need:

Now if you didn't make whatever you are making make sure you have EXPRESS WRITTEN CONSENT from whoever did. Make sure to give them credit too. For example, Garry Newton made this and I got his permission to make a mold of this for my mom. Don't just buy someone else's work and try to remake it and pass it off as your own. If you do this is called recasting and it is a terrible, terrible thing.

Anywho, I like to stick my items to something portable. This is a piece of sintra, but wood works too. That way I'm not confined to working in one area. Make sure you use something that doesn't succumb to moisture like cardboard does.

You will also need something to make a mother mold. I used hydrostone, but plaster and fiberglass work and they make a bunch of different materials specifically for making master molds. Master molds are used with soft molds so that when you are casting into the soft mold, the finished piece isn't deformed. A bad mother mold means that you get bad castings. Take your time with it. I didn't do a great job but do as I say, not as I do.

Now that you have everything, what do you do?

The first thing you want to do is put soap in the water. Use it liberally. It's better you put too much soap in than not enough. This is very important. The soap serves two purposes. The first is that it keeps the silicone from sticking to your glove. The second is that the soap acts as a catalyst and makes the silicone cure in about 15 minutes as opposed to 2 hours. I don't know why it does, but it just does. If you don't use soap, this process can take a whole lot longer.

Now that you've got the water all soapy, it's time to put on your gloves. I use one glove on my left hand (since I'm right handed) and I leave my right hand free to use the caulk gun.

Wet your glove with the soapy water. This will keep the silicone from sticking to your glove. Otherwise, you make a big, gooey mess.

Put a little less than a golf ball sized clump of silicone in your hand. I put it in my hand out of the cup so you could see a little better, but it's best if your hand is in the soapy water and the silicone goes into the soapy water before touching your glove.

Alternatively, if you have a wider container than this glass you can put it directly into the water and scoop it up. This is how I spilled most of my water, and I don't prefer to do this, but it does work if that floats your boat.

Wad your silicone into a small ball. Don't press too hard, it doesn't take much pressure. I've found it also works better to use a rolling method rather than a pressing one. What this does is it makes your silicone more manageable, but also ensures that there are no sticky parts of the silicone (showing that the silicone was fully coated in the soap).

After your silicone is sticking into a nice ball apply it to the surface of the object. Make sure that you don't apply it thicker than 1/8". This silicone cures when the acetic acid evaporates. If you layer it on too thick, the top layer will cure trapping a layer of uncured gooey silicone.

This is what happens when you put it on too thick. When you touch the surface you can feel that there is uncured silicone trapped underneath. It is much easier if you don't put it on too thick, but if you do I've found a pretty good solution. Basically, you lance the spot where it is wet and squeeze out all of the uncured silicone. You are then left with a pocket of air. This is very bad for molds. If you cut the top of the "skin" off so the spot that had the uncured silicone is exposed, you can take the uncured silicone and squish it back on (not too thick) and fix the pothole. Imagine lancing a blister and covering it with a band-aid.

Repeat for the second layer, thickening the mold.

This is the third and final layer. I used it to smooth out the mold and make it nice and form fitting. Normally this would be the layer where you would add keys for the mother mold, but this has a fairly distinct shape and I wasn't too concerned about the mother mold fitting on to the soft mold. Also, depending on the size of the object you may need more than three layers.

Now that the mold is ready for the mother mold, I built a divider so I can make a mother mold that will allow the final piece to come out. The reason for a two part mold is that this piece has undercuts. If I made a one part mother mold, I wouldn't be able to get the solid cast piece out of the mold so we make it in two pieces.

After the first side is finished curing, remove the cardboard and coat the first half with Vaseline. This is important, because you don't want the mother mold sticking to itself.

After both sides are done, you can pull out the original and you are done.

Voila! The rest of the images are of the mother mold and the original pulled out of the mold.

There you go. I spent all of 10 bucks to get all the stuff, and most of it will last for future use.

This method can get some pretty excellent detail. I would only recommend using this on smaller items, but it can be used on larger items. For example I used this method when I made these:

And of course there are pros and cons to this as with any method.

Pros:
-Cheap in small batches
-Easy to work with
-Fast curing
-Easy to obtain
-Good for small items

Cons:
-More Expensive on a large scale
-Molds tear relatively easily (you could reinforce the silicone by adding a layer some burlap to the second layer while it is still tacky
-Smells bad
-Since you are using soapy water, this method can trap water on the surface of what you are making. This is great if you are molding over plaster or fired clay, but less great if you are using dry unfired clay as the details can get washed away or if you use something non porous as water bubbles can get trapped on the surface of the mold if you aren't careful.

hiya this looks like it would work really well. i was planning on using this technique for creating a mold of my metal sword so that way i could recreate it as a plastic replica. will the mix stick to metal? and how would i go about cutting the mold into two pieces? and after that what should i use to fill the mold to create it in a sturdy durable plastic? thank you very much

@sephykilluYou should make the mold in 2 pieces. Use clay and build a divider half way up and make the top of th mold. Then build a mother mold for the top. Flip it over, remoce the clay and make the bottom mold and mother mold. Make sure to add keys to the top and bottom so they line up when you are casting. If you are molding an actual sword, you may also want to add a rigid core to your cast. A cast that thin will be flexible and break easier than anyone would like for a prop or replica.

thank you very much. the only thing i am planning on replicating is the blade itself which is very thin. would that be a problem and i didnt understand what you meant by adding a rigid core to the cast. i only need to make a mold that will last 1 fill. what should i use to fill the cast when i make it?

Since the blade is so thin, casting it in resin or something other than metal(which at that thickness would still be flimsy when it's cast) would be difficult and may not work out so well. What I meant by rigid core is some fiberglass or metal rod/strip running the length of the blade and would stick out enough to secure the blade to the handle. This would be similar to the way a boffer has a rigid PVC or fiberglass core surrounded by foam. It serves to strengthen the blade and keep it from drooping or deforming.

Casting swords is, in general, a bad idea. As far as my experience has taught me, when you make a sword the blade will be thicker than that of a real sword (unless it's a thick sword like a bastard or great sword). The thicker blade allows more stability and rigidity when you cast it. With an object as thin as a sword, even with a rigid core, the cast blade probably won't turn out the way you want. It will be so thin that it will deform under it's own weight.

As far as casting, I generally use fiberglass resin and matte that you can find at Home Depot or Lowes. It's more convenient than ordering resin online, but it's a pain to work with and pretty hazardous to your health. It's usually in the isle next to the spray paint and is normally found next to the caulk. You could use fiberglass and resin to make a blade, but it would take a lot of care and work and might be a little costly. Alternatively, you could use the blade as a template and shape a wooden blade. It would probably be thicker and pretty heavy, but if you get a hard wood you should be good.

It really depends on what you need the sword for. If it's for a convention, check the rules of the convention as to what they allow. If it's for your own personal collection, save yourself some trouble and go to Home Depot and get some Aluminum or steel strips and JBweld those suckers together and make a metal blade. But only if you don't want to take a real sword anywhere...

Also just an FYI, you may be new to this, but make your mold like it will make more than one cast. Even if you don't, breaking your mold intentionally is usually a bad idea. You usually end up making more work for yourself than if you took an extra hour making a good mold, plus if you destroy the mold and something happens to the first cast you are out of luck. Besides, if you go in to making the mold with the mindset of multiples you will make a cleaner mold that will be easier to work with.

thank you very much. the reason i am trying to make it out of plastic is im going to a convention where any kind of metal sword is prohibited and from experience it is dodgy with wood. i think you have to keep it sheathed if it is wood. but if it is made of plastic you can take it out all you want. so i wanted to make it out of plastic so i could repeatedly take the sword out for aesthetic purposes. but it sounds like a wood replica might be my only option. as for making it out of wood. i could probably spray it with primer and then chrome to make it look real right? i just don't want to be hassled year after year about the convention policies.

Right. Make sure it's rigid plastic, like acrylic or something. If you are unsure call and ask or go in and ask. You can take two pieces and bevel the edges and then glue them together to make the taper that a blade would have. That would be easier than trying to sand down to the middle of a single piece. It is possible to sand the center groove with a Dremel. If you don't have one, get a wooden rod (square rod will work best) and cut a 45 degree angle on the tip. Then attach sandpaper to the tip and use that to sand the channel down the middle. Take your time with this sword, if you rush it won't look good.

Is this mold flexible? For example if you have a fragile sculpture with many undercuts will the mold come off the sculpture with its flexibility? Also if you have an unfired 3 dimensional clay head would this method work. And one last question can this mold cast plaster or cement? Thank you so much. I love this idea. :)

thank you so much! ^_^ I will be trying this, this week, I've seen a different method where instead of squirting the silicone into the soap and water mixture, you squirt a line on your sculpture and with your finger (which was already soaked in soap water) you dap it/spread it getting rid of air bubbles. You repeat this until the whole sculptures covered. Then you put one more layer after its dried. Would you recommend your method of dumping the silicone in the soap water, or the other method with the squirting and dabbing. Thank you. :)

I'm looking for an affordable way to make gloves for my costume. I would love to know if there is a similar process that I can make for scary hands/gloves. I was curious if I could put on latex gloves and pour silicone over my hands if I could make gloves like that will that work? Any suggestions would be greatly appreciated.

You could do that, but I don't recommend it. Keep in mind that this is not meant to be used on human skin. There are chemicals in the caulk to prevent mold from growing which is not good for people. Also the way this caulk cures, acetic acid evaporates and leaves the silicone. If you stick that on your body, your body will absorb all of that acetic acid.

I would suggest making a mold from alginate and then a solid cast. You can then make a more rugged mold from the cast hand. Alginate is very weak and basically one time use.

If you are set on applying it directly to your body (which will not feel good if you have any hair) look at higher grade skin latex or aquarium grade silicone caulk.

The silicone can stand heats up to the ballpark neighborhood of 800 degrees F. That means you could cast low melt temp metals like pewter or lead(don't cast lead, it's bad for you). If you are wanting to cast anything hotter than that shell out the money for higher quality silicone. If you are going to cast hot material do a small scale test though to make sure you get the results you want.

I'm planning on making a silicone mold of a lawn jockey, around 4 feet tall. Would this method work with a piece that large? It'll be a two piece mold with backing material. (probably plaster) I'll be casting the replicas in concrete, and possibly in epoxy resins later. Do you have any experience with resin? I've always worked with clay in press molds and admit I'm a newbie with other materials.

For something that large I would go ahead and buy smooth on rebound 25. It will save you money and will be easier to use.

http://www.smooth-on.com/Platinum-Cure-Sili/c1115_1132/index.html

I have experience with resin and for an item like that you'll want to slush cast it. A solid casting that big is going to cost a lot and be hard to deal with. The size will be a problem though because it will be hard to slush cast something almost as big as a person.

You could open cast the two halves and bring them together with resin after you have the two halves.

i dont have that much money to be throwing on expensive silicone molds and resin and this looks perfect...I was thinking of making gun/rifle props out of parts that are asembled together, what do you think is the best resin to use in this kind of mold?

You can use the resin that they sell in Home Depot or Lowes for repairing cars or boats. The only thing about the resin they sell is that it is nasty to work with. It stinks and is meant to be used with fiberglass mat or cloth. It's cheap, but not so great to work with. You could go with something from Smooth-On. They have a wide selection of resins and I like SmoothCast 320 or SmoothCast Onyx:http://www.smooth-on.com/Urethane-Plastic-S/c1120_1325/index.htmlhttp://www.smooth-on.com/Urethane-Plastic-S/c1120_1210/index.html

It all depends on what you want to spend and what quality of product you want to put out.

I'm absolutely 100% new to making molds. I'm trying to get started, and so I've been doing a lot of research on what I need to buy. However, almost none of the sites I've been to has what their original model is made out of. One of my friends who does props for a living has told me that she uses clay for her original model and makes the mother mold from that. But I just want to make sure for certain that if I used clay and molded that, that it would be fine.

The reason why I'm hoping to make the models out of clay is because I'm used to sculpting with clay and it's relatively expensive. If you have a better alternative than clay that's more cost effective that you personally use, I'd be more than happy to try that out. I'm just starting out completely new and want to make sure I do everything right.

Most of the sites are pretty vague about what they are molding because it can be anything really. There are some things that are impossible to mold, like pine cones or feathers, but you can make a mold of most things.

What you use to sculpt is mostly a matter of what medium you are most comfortable with, as well as what you are sculpting. If you are making a replica gun or knife (something very rigid and precise) it would probably be better to use wood or MDF. Does that mean you can't sculpt a dagger out of clay? No, but I don't particularly recommend it.

As far as clay goes, there are a few kinds you can use.

First, what I use 80% of the time, is the kiln fire white or red clay. This is the stuff that is used in traditional ceramic making, and let me tell you it is dirt cheap. That's the biggest draw for me. Spending less than $30 on 50 lbs of clay is awesome, but it has it's limitations. This stuff is not good for long term sculpts. If you are working on something for a long time, this stuff is a pain to keep workable. It also is difficult to get varying levels of firmness on the clay, and this goes back to keeping the clay moist. Also, since this is water based clay, this process of mold making can degrade fine surface texture since you are wetting the silicone.

Next you have oil based clays. Go with sulfur free if you go this route. Sulfur interferes with the curing of platinum-cure and other high end silicone, so if you want to make a silicone mask, sulfur would ruin the pour. This is mostly just a matter of buying the right stuff. This stuff also comes in different levels of firmness, with firm capturing the greatest detail. And the biggest draw for this type is that it doesn't dry out. Downside, depending on where you buy it, can be as much as $80 for 25 lbs.

There are other kinds of clay like sculpey, but I don't really recommend them for the blank. One of the great things about mold-making is you can use just about anything you have available.

Since you are looking for cost effective, I would use water based clay. It's cheap and easily found if you have a clay store (I like Armadillo Clay in Austin) but you can also find it at Hobby Lobby if you have to. Some of the other stuff you would probably have to place an online order.

I used clay for my Professor Pyg mask, and you should look at that post if you want to see an example of clay for a mold base.

Let me know if you have any more questions or if I wasn't clear on anything.

hi there. i have a commissioner wanting me to make some guns and i was planning to use this method to cast them (because the character has 4 guns. i am not making 4 freaking guns) and there are parts of this design that need to be hollow. (namely the barrels and a pocket im creating in the original positive to house speakers that make gun noises when a button is pressed behind the trigger) and i was wondering if this method could accomidate that? would the silicone be strong enough to hold through making multiple casts? or would the negitives from the hollow parts tear when you are demolding?

Your problem is really two issues. Making a hollow casting and casting multiple times.

As far as casting multiple times, this method should hold up of multiple castings if you make a good mold. Make it thick, strengthen it with fabric (like burlap) and most importantly plan out your mold and make it complicated enough so you can reduce the chances of it tearing. If you do this, it should withstand four castings. The only thing you might have problems with is if you have extreme surface detail, that might get lost after a few castings, and if you cast with a high temperature resin, there is a chance that parts of it might get stuck to the casting and not separate (which you might be able to avoid with a good mold release). The good thing about this is it's so cheap you could just make another mold if you had to.My molds rip all the time, but I'm usually lazy and make less complicated molds than I should for single castings.

Basically, this part comes down to how well you've constructed your mold.

To answer the other part of your question, I would do a slush mold to make a hollow gun part, and probably cast the guns in separate parts (at least barrel and grip) or make an access panel (for batteries and adding the speakers. The way you would make a slush mold is to do a two (at least) parted mold and not create a sprue or pour spout. Then instead of casting by pouring the resin in and making a solid casting, you pour a set amount of resin in the mold and close it up. You then slush and swirl the resin around until it sets and leaves an even coating on the inside of the casting and you now have a hollow casting.You can now add all the internals to said hollow cast.

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Lots of thanks to you for advice for making moulds easily and without spending so much money and time.I am also working in a China Mould Manufacturer company . I must apply your suggestions for Mould Manufacturing.

Nice images with description you have posted in your blog. I am very happy to be found such type of blog after huge searches through online. You have mentioned about Cheap molds.This information is very interesting, I really enjoyed. Thanks for sharing!

Do you think I could use a real leaf, maybe coated in spray cooking oil to keep it from sticking, and then layer the silicon on it? I want some reusable leaf molds to use when making hypertufa stepping stones and leaves. Thanks for any thoughts you may have and thanks for the great info!!

Hello! I'm considering taking up casting with epoxy resins among other things, and I am hella confused about mold-making. For example, I want to make a replica of Keening from TESIII Morrowind and I do not know where to start. I've thought about the possibility of making multiple parts out of clay or something similar, making molds of individual parts, and then fitting the pieces together somehow. I was curious if there's any tips or advice you can give me as far as methods and materials to buy for both the molding and the casting, as well as removing the molds. Are the molds one-time use only? For example, keening has little spikes all over it, and I'm confused how one would remove the clay without compromising the mold.Thank you!